Author(s) from Durham

Abstract

The ‘optimal’ factorization scale μ0μ0 is calculated for open heavy quark production. We find that the optimal value is μF=μ0≃0.85p2T+m2Q−−−−−−−√μF=μ0≃0.85pT2+mQ2 ; a choice which allows us to resum the double-logarithmic, (αslnμ2Fln(1/x))n(αsln⁡μF2ln⁡(1/x))n corrections (enhanced at LHC energies by large values of ln(1/x)ln⁡(1/x) ) and to move them into the incoming parton distributions, PDF (x,μ20)(x,μ02) . Besides this result for the single inclusive cross section (corresponding to an observed heavy quark of transverse momentum pTpT ), we also determined the scale for processes where the acoplanarity can be measured; that is, events where the azimuthal angle between the quark and the antiquark may be determined experimentally. Moreover, we discuss the important role played by the 2→22→2 subprocesses, gg→QQ¯gg→QQ¯ at NLO and higher orders. In summary, we achieve a better stability of the QCD calculations, so that the data on cc¯cc¯ and bb¯bb¯ production can be used to further constrain the gluons in the small x, relatively low scale, domain, where the uncertainties of the global analyses are large at present.